Many medical procedures are performed using minimally invasive surgical techniques, wherein one or more slender implements are inserted through one or more small incisions into a patient's body. Catheters are increasingly used to access remote regions of the human body to deliver diagnostic or therapeutic agents or for the treatment of biological tissue. Catheters which use the cardiovascular system as the pathway to a treatment site, for example, are especially practical.
In many applications, the catheter delivers therapeutic agents or applies energy-based principles to the tissue based on the transfer of fluid through the catheter. In tissue ablation, for example, the surgical implement is a catheter that can include a rigid or flexible structure having an ablation device at or near its distal end that is placed adjacent to the tissue to be ablated. Radio frequency energy, microwave energy, laser energy, extreme heat, and extreme cold can be provided by the ablation device to ablate the tissue. In other applications, regional anesthesia can be applied by using such surgical instruments. In still other applications, diagnostic or therapeutic agents can be delivered to a treatment site by way of a catheter.
Often the treatment area which one desires to access by catheter is within a soft or muscular tissue such as the liver, brain, veins and arteries, biliary ducts or ostia, or the heart. These are difficult sites to reach. The catheter must be introduced through a biological cavity, for example, a large artery such as those found in the groin or the neck and then be passed through narrowing regions of the cardiovasculature until the catheter tip reaches the selected site. Often such biological passageways wind and loop or are otherwise tortuous. Catheters for such applications are difficult to design, since they must be fairly stiff at their proximal end to allow passage of the catheter tip through the loops and increasingly smaller passageways and at the same time not cause significant trauma to the passageway and further be flexible enough to navigate the passageway.
Examples of catheters designed to meet these criteria are disclosed in the art. Often, the catheter shaft is made with a flexible material to permit it to navigate the passageway used to reach a treatment site. Since many catheter-based applications involve the transmission of a therapeutic agent or fluid from the catheter's proximal to distal end for applications at the treatment site, the shaft of the catheter often has internal lumens that permit the delivery or return of a particular therapeutic agent or fluid. For example, cryosurgery catheters have internal lumens that deliver refrigerant to the catheter tip for treatment and exhaust the refrigerant from the tip. Owing to the properties of the catheter that make it flexible, however, kinks may still form in the catheter shaft during use when the shaft is bent beyond its minimum bend radius or kink radius.
Solutions advanced in the catheter arts generally place metal braids or wires at the outer wall of the catheter shaft to reduce the likelihood of a kink forming. But such catheters still kink when the catheter is bent beyond its kink radius during use. When a kink forms in the catheter shaft during use, the passage, or the internal lumens within the shaft, can become obstructed, and the flow of a therapeutic agent or fluid can be interrupted.
It is therefore desirable to provide a device that resists or prevents such kink-related obstructions and interruptions in fluid or agent delivery.